Refrigerant displacement apparatus with thermal protection device

Abstract: A scroll type compressor in which the discharge chamber is divided into two chambers by a dividing wall (283,293,303) which surrounds a bore (274) communicating the discharge chamber with a fluid pocket near the centre of the scroll members (27,28). The wall (283,293,303) has an opening (283a,293a,303a,303b) which faces a thermally sensitive area (123) in the wall of the compressor housing (10). A thermal sensor (60) is positioned behind the thermally sensitive area.

Description: This invention relates to a fluid displacement apparatus, and more particularly, to an improvement in a thermal protected device in a fluid displacement apparatus. A scroll type fluid displacement apparatus is well known in the prior art. For example, U.S.Pat.No.4,411,604 issued to Terauchi discloses a basic construction of a scroll type fluid displacement apparatus. Generally, in the conventional refrigerant compressor, when the temperature of an compression refrigerant gas excessively rises, the compressor failure to normally operates per se since each parts of the compressor become to take a thermal expansion and increase a friction each other. Particularly, it is a problem in durability of the compressor that the temperature of a compression refrigerant gas at the center of a scroll excessively rises. The one contempt solution to the above problem is the use of a protected device which intermits the operation of the compression through the electromagnetic clutch by means of perceiving a temperature of the refrigerant gas when the compression gas rise to a predetermined temperature. Referring to Figure 1 and 2, a scroll type fluid displacement apparatus in accordance with the prior art is shown in the form of scroll type refrigerant compressor unit 1. Compressor unit 1 includes housing 10 having front end plate 11 mounted on cup-shaped casing 12. Opening 111 is formed in the center of front end plate 11 for penetration or passage of drive shaft 13. Annular projection 112 is formed in a rear end surface of front end plate 11. Annular projection 112 faces cup-shaped casing 12 and is concentric with opening 111. An outer peripheral surface of annular projection 112 extends into an inner wall of the opening of cup-shaped casing 12 so that the opening of cup-shaped casing 12 is covered by front end plate 11. O-ring 14 is placed between the outer peripheral surface of annular projection 112 and the inner wall of the opening of cup-shaped casing 12 to seal the mating surfaces of front end plate 11 and cup-shaped casing 12. Annular sleeve 15 projects from the front end surface of front end plate 11 to surround drive shaft 13 and defines a shaft seal cavity, and is formed separately from front end plate 11. Therefore, sleeve 15 is fixed to the front end surface of front end plate 11 and sleeve 15. Alternatively, sleeve 15 may be formed integral with end plate 11. Drive shaft 13 is rotatably supported by sleeve 15 through bearing 18 located within the front end of sleeve 15. Drive shaft 13 has disk 19, at inner end thereof, which is rotatably supported by front end plate 11 through bearing 20 located within opening 111 of front end plate 11. Shaft seal assembly 21 is coupled to drive shaft 13 within the shaft seal cavity of sleeve 15. Pulley 22 is rotatably supported by bearing 23 which is carried on the outer surface of sleeve 15. Electromagnetic coil 24 is fixed about the outer surface of sleeve 15 by supporting plate 25 and is received in annular cavity of pulley 22. Armature plate 26 is elastically supported on the outer end of drive shaft 13 which extends from sleeve 15. Pulley 22, magnetic coil 24 and armature plate 26 form a magnetic clutch. In operation, drive shaft 13 is driven by an external power source, for example the engine of automobile, through a rotation transmitting device such as the above explained magnetic clutch. A number of elements are located within the inner chamber of cup-shaped casing 12 including fixed scroll 27, orbiting scroll 28, a driving mechanism for orbiting scroll 28 and rotation preventing/thrust bearing device 35 for orbiting scroll 28. The inner chamber of cup shaped casing 12 is formed between the inner wall of cup shaped casing 12 and the rear end surface of front end plate 11. Fixed scroll 27 includes circular end plate 271, wrap or spiral element 272 affixed to or extending from one end surface of end plate 271 and internal thread bosses 273 axially projecting from the other end surface of end plate 271. Internal thread boss 273 includes first rib portion 273a and second rib portion 273b formed to be faced radially each other and surrounds discharge port 274. Further, internal thread boss 273 includes first notch portion 273c and second notch portion 273d formed to be faced radially each other and surrounds discharge port 274. An axial end surface of internal thread boss 273a and 273b are sealed on the inner end surface of bottom plate portion 121. Both internal thread boss 273a and 273b are provided with tapped holes 254 for receiving bolts 37. The wall portion between tapped holes 254 is formed for the purpose of reinforcing tapped holes 254. Bottom plate 122 of cup-shape casing 12 is fixed to fixed scroll 27 by bolt 37 which screw into tapped holes 254 of internal thread boss 273a and 273b. Thus, fixed scroll 27 is fixed within the inner chamber of cup-shaped casing 12. Circular end plate 271 of fixed scroll 27 partitions the inner chamber of cup shaped casing 12 into front chamber 29 and rear chamber 30. Seal ring 31 is disposed within a circumferential groove of circular end plate 271 to form a seal between the inner wall of cup shaped casing 12 and the outer surface of circular end plate 271. Spiral element 272 of fixed scroll 27 is located within front chamber 29. Cup-shape casing 12 is provided with a fluid inlet port 36 and fluid outlet port 39, which are connected to rear and front chamber 29 and 30, respectively. Further, cup-shaped casing 12 is provided with senser pocket 122 in which thermal protector 60 is disposed. Thermal protector 60 is a protected device which intermits an operation of a compressor by perceiving a temperature of a compression refrigerant gas. This compression refrigerant gas strikes against thermal sensitive area 123 formed on an inner surface of cup-shape casing 12 corresponding to the bottom of senser pocket 122 of bottom plate portion 121. A hole or discharge port 274 is formed through circular end plate 271 at a position near the center of spiral element 272. Retainer 50 and reed valve 38 are fixed together to circular end plate 271 by bolt 51. Reed valve 38 closes discharge port 274. Orbiting scroll 28, which is located in front chamber 29, includes circular end plate 281 and wrap or spiral element 282 affixed to or extending from one end surface of circular end plate 281. Spiral elements 272 and 282 interfit at an angular offset of 180 and at a predetermined radial offset. Spiral elements 272 and 282 define at least one pair of sealed off fluid pockets between their interfitting surfaces. Orbiting scroll 28 is rotatably supported by bushing 33 through bearing 34 placed between the outer peripheral surface of bushing 33 and the inner surface of annular boss 288 axially projects from the end surface circular end plate 281. Bushing 33 is connected to an inner end of disk 19 at a point radially offset or eccentric of the axis of drive shaft 13. Rotation preventing/thrust bearing device 35 is disposed around the outer peripheral surface of boss 282 and placed between the inner end surface of front end plate 11 and the end surface of circuit end plate 281 which faces the inner end surface of circular end plate 281 which faces the inner end surface of front end plate 11. Rotation preventing/thrust bearing device 35 includes fixed ring 351 attached to the inner end surface of front end plate 11, orbiting ring 352 attached to the end surface of circular end plate 281, and a plurality of bearing elements, such as balls 353, placed between the pocket formed by rings 351 and 352. Rotation of orbiting scroll 28 during orbital motion is prevented by the interaction of balls 353 with rings 351,352. The axial thrust load from orbiting scroll 289 also is supported on front end plate 11 through balls 353. In this arrangement, the compression refrigerant gas exhausted from discharge port 274 radially flows out and branches into two flows through first notch portion 273c and second notch portion 273d as an arrow in Figure 2. Further, each of the refrigerant gas streams flowing along the inside surface of the cup-shape casing 12 merge in one flow at fluid outlet port 39 and this flow is exhausted from fluid outlet port 39 to outside of the compressor. In this time, the temperature of the compression refrigerant gas is measured by thermal protector 60 disposed in sensor pocket 122. Thermal protector 60 only perceives one compression gas flow which is flowed clockwise from second notch portion 273d and scarcely perceives the other compressor gas flow which flows counter clockwise from first notch portion 273c. Thereby, there is a difference between an actual temperature of a compression gas and the temperature perceived by thermal protector 60. As a result, to perceive an approximate value to an actual temperature of a compression gas is considerably difficult in this arrangement. US-A-5118260, US-A-4265603 and GB-A-2207704 all disclose compressors in which thermal sensors are provided. It is an object of the invention to provide a fluid displacement apparatus with an improved thermal protected device which exactly perceives a temperature of a fluid. US-A-4477238 discloses a fluid displacement apparatus comprising a housing having a fluid inlet port and a fluid outlet port, further defining first chamber in which successive strokes of sucking, compressing, and discharging a fluid are repeatedly performed; a fluid port communicating the first chamber to a second chamber; and a dividing wall disposed in the second chamber for partitioning the second chamber into two sub-chambers and circularly surrounding the fluid port; and according to the present invention, such an apparatus is characterised by a recessed portion formed in the housing adjacent to the fluid outlet port for accommodating a thermal sensor device, the thermal sensor device perceiving a temperature of a thermally sensitive area against which fluid strikes, the thermally sensitive area being formed on an inner surface of the housing corresponding to a bottom of the recessed portion of the housing; and directing means disposed in the second chamber for directing the fluid towards the thermally sensitive area of the housing. Thereby, the greater part of a compression fluid strikes against the thermal sensitive area before flowing out of the apparatus through the fluid outlet port. Further objects, features and other aspects of this invention will be understood from the following detailed description of the preferred embodiment of this invention referring to the annexed drawings. In the accompanying drawings: Figure 1 is a cross sectional view of a scroll compressor in accordance with the prior art, Figure 2 is a cross sectional view taken along line 2-2 of Figure 1. Figure 3 is a cross sectional view taken along line 2-2 of Figure 1 in accordance with a first embodiment. Figure 4 is an enlarged view of a scroll type compressor, illustrating the first embodiment construction of a thermal protector device. Figure 5 is a cross sectional view taken along line 2-2 of Figure 1 in accordance with a second embodiment. Figure 6 is an enlarged view of a scroll type compressor, illustrating the second embodiment construction of a thermal protector device. Figure 7 is a cross sectional view taken along line 2-2 of Figure 1 in accordance with a third embodiment. Figure 8 is an enlarged view of a scroll type compressor, illustrating the third embodiment construction of a thermal protector device. A following embodiments of the present invention as applied to a scroll type compressor for use in a refrigerant circuit are illustrated in Figures 3-8. The same numerals are used in Figures 3-8 to denote the corresponding elements shown Figure 1 and 2, and the explanations of those elements are omitted. Figure 3 and 4 illustrate a first embodiment of the invention. Cup-shaped casing 12 is provided with senser pocket 122 in which thermal protector 60 is disposed. Senser pocket 122 of cup-shaped casing 12 is formed to be shaped as a hollow extending from the outer surface of cup-shaped casing 12 to the center of the compressor and to be adjacent fluid outlet port 39. The thickness between bottom surface 122a of senser pocket 122 and thermal sensitive area 123 which is a portion of bottom plate portion 121 is designed to be a predetermined value, about 3-6 mm. Fixed scroll 27 includes internal thread boss 283 axially projecting from the other end of end plate 271 thereof and circularly surrounded discharge port 274. An axial end surface of internal thread boss 283 is sealed on inner surface 121a of bottom plate portion 121. Furthermore, internal thread boss 283 includes one notch portion 283a formed between tapped holes 254 and radially facing to thermal sensitive area 123 of bottom plate portion 121. The radial width of notch portion 283a is formed to be almost same as that of bottom surface 122a of senser pocket 122. Further, the axial depth of notch portion 283a spreads from one end surface of end plate 271 to thermal sensitive area 123. In this arrangement, the compression gas exhausted from discharge port 274 flows from notch portion 283a to thermal sensitive area 123 of bottom plate portion 121 as arrow in Figure 3. Thereby, the greater part of compression gas strikes against thermal sensitive area 123 before flowing out the compressor through fluid outlet port 39. Therefore , thermal protector 60 can perceive an approximate value to an actual temperature of the compression gas in comparison with the prior art. Further, the operation of the compressor is intermitted at accurate temperature of a compression refrigerant gas by thermal protector 60 before the temperature of a center of scroll excessively rises. As a result, durability of the compressor is improved. Figure 5 and 6 illustrate a second embodiment of the invention. Internal thread boss 293 includes one opening 293a formed between tapped holes 254 and radially facing to thermal sensitive area 123 of bottom plate portion 121 and shaped as a cylindrical hole. radial diameter D of opening 293a is formed to be almost same as diameter R of the bottom surface of senser pocket 122. Further, the line radially penetrating the center of opening 293a is identical to other line radially penetrating the center of senser pocket 122. Figure 7 and 8 illustrate a third embodiment of the invention. Internal thread boss 303 includes one passage 303a formed between tapped holes 254 and radially facing to thermal sensitive area 123 of bottom plate portion 121. Further, internal thread boss 303 includes projection portion 303b extending from opening 303a to thermal sensitive area 123. Thereby, the compression refrigerant gas facilitates to flows and strike against thermal sensitive area 123 because of being guided by projection portion 303b as compared with the previous embodiments. Both functions and effects of these embodiment are almost same as the function and the effects of a first embodiment so that explanations thereof are omitted.

Claims: A fluid displacement apparatus comprising a housing (10) having a fluid inlet port (36) and a fluid outlet port (39), further defining first chamber in which successive strokes of sucking, compressing, and discharging a fluid are repeatedly performed; a fluid port (274) communicating the first chamber to a second chamber; and a dividing wall (283,293,303) disposed in the second chamber for partitioning the second chamber into two sub-chambers and circularly surrounding the fluid port (274); characterised by a recessed portion (122) formed in the housing (10) adjacent to the fluid outlet port (39) for accommodating a thermal sensor device (60), the thermal sensor device perceiving a temperature of a thermally sensitive area (123) against which fluid strikes, the thermally sensitive area being formed on an inner surface of the housing corresponding to a bottom of the recessed portion (122) of the housing; and directing means (283a,293a,303a,303b) disposed in the second chamber for directing the fluid towards the thermally sensitive area (123) of the housing (10). An apparatus according to claim 1, wherein the directing means (283a,293a,303a,303b) causes the fluid to flow directly towards the thermally sensitive area (123). An apparatus according to claim 1 or claim 2, wherein the directing means (283a,293a,303a,303b) is an opening in the dividing wall (283,293,303) which faces the thermally sensitive area (123). An apparatus according to any one of the preceding claims, wherein the directing means is a passage (283a,303a,303b). An apparatus according to claim 4, wherein the passage (283a,303a,303b) is opposite to the thermally sensitive area (123) of the housing (10). An apparatus according to any one of claims 1 to 3, wherein the directing means is a cylindrical hole (293a), An apparatus according to claim 6, wherein the cylindrical hole (293a) is opposite to the thermally sensitive area (123) of the housing (10). A scroll type compressor including an apparatus according to any one of the preceding claims, wherein the fluid is a refrigerant gas, and further comprising a fixed scroll member (27) fixedly disposed relative to the housing (10) and having first end plate (271) from which a first wrap extends (272); an orbiting scroll (28) having a second end plate (281) from which a second wrap (282) extends, the first and second wraps interfitting at an angular and radial offset to form a plurality of line contacts to define at least one pair of sealed off fluid pockets; a driving mechanism including a drive shaft (13) rotatably supported by the housing and a drive pin eccentrically extending from an inner end of the drive shaft; a discharge chamber providing the second chamber located inside of the compressor housing (10) and adjacent to the fixed scroll member (27) on the side of the first end plate (271) opposite the side thereof from which the first wrap (272) extends, the first end plate having a discharge bore (274) providing the fluid port therethrough communicating between a fluid pocket providing the first chamber near the centre of the first wrap (272) and the discharge chamber; the dividing wall (283,293,303) having reinforcing tapped holes (254) formed thereof and surrounding the discharge bore (274), the tapped holes received binding members (37) which bind the fixed scroll (27) to the housing (10); wherein the directing means is formed in the dividing wall (283,293,303). A scroll type compressor according to claim 8, wherein the directing means is an opening (283a,293a,303a,303b) which is radially opposite to the thermally sensitive area (123) of the housing so that a first line radially penetrating a centre of the opening is substantially collinear with a second line radially penetrating a centre of a bottom surface of the recessed portion (122).

Inventors: SATO TADASHI, SATO, TADASHI
Applicants: SANDEN CORP, SANDEN CORPORATION
Application year: 1994
Main classification: F04C29
IPC codes: F04C29, F04C18, F04C28